<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style type="text/css">
*{
    padding:0;
    margin:0;
}
.menu {
    width: 120px;
    background-color: #CCC;
    position: relative;
    height: 26px;
}
.menu .sub {
    position: absolute;
    display:none;
    left: 0px;
    top: 26px;
    background-color: #9CF;
    width: 100%;
}
</style>
<script src="jquery-2.0.0.min.js"></script>
<script>
$(function(){
    $('.menu').mouseover(function(e){
      $(this).find('.sub').stop().toggle(1000);
    });
    $('.menu').mouseout(function(e){
      $(this).find('.sub').stop().toggle(1000);
    });
});
</script>
</head>

<body>
<div class="menu">
<span>按钮</span>
<dl class="sub">
<dd><a href="">选项1</a></dd>
<dd><a href="">选项2</a></dd>
<dd><a href="">选项3</a></dd>
</dl>
</div>
</body>
</html>